Mechanical face seals in my opinion are better in most applications. As always it depends upon the application. Lip seals leak more, the elastomers can age faster, and in the case of a catastrophic failure cannot control leakage as well as a mechanical seal. Lip seals, however; are cheaper, and easier to install.
Mechanical seals can be engineered for many more applications than lip seals can. Higher temperatures, more corrosive fluids, and higher pressures can be sealed with mechanical seals than lip seals.
We have been aplying face seals for bearing protection and the results are excelent! They have a lower wear rate, and protect the bearing against contaminants.
For what its worth I understand your question and reasoning. I believe in most cases a face seal is better, however I think Longeron is correct, seals for the most part are determined by the application. The real problem with the original design is a manufacture of a piece of equipment wants the lowest standard cost available. This could increase the gross margin or lower the sales price for the manufacture. On the other side of the desk an end user wants the highest quality or least amount of problems with the operation. This only leaves two questions:
1) Manufacture:
How do you convince a purchasing agent the higher initial cost will benefit him in the long term?
2) End User:
How do you convince the manufacture to incorporate two designs in their product (increase standard cost) so you can use quality when the rest of the manufacturing world only considers initial cost?
I guess these two questions are relative to anything.
The answer to your first question is generally that you can't. There is no real reason for the pump OEM to give the end user a higher quality pump seal. It is another point where cost savings can be achieved. Most pump OEMs are not in the seal business. They pretend to be sometimes. However, if the pump OEM is also a seal OEM, things can be turned around. The obvious example should be Flowserve. If the end user doesn't specify another make of seal, Durco, IDP, Pacific, and the rest of the conglomeration should spec out the best Dura, Five-Star, or BW/IP seal they can. Then all they have to do is pass on the end user info to the local seal rep and they have all the repair or upgrade business.
(I just hope some higher up in Flowserve doesn't read that)
As for part two; the seal, pump, and bearing reps should be making it a point to say to the end users that the best thing they can do to improve the mean time between repair and decrease maintenance costs is to spec themselves the best parts for the application, or have the respective parts rep spec out the best parts. Why would the bearing rep have anything to gain by suggesting the worst bearing for an application? He wouldn't. Who would buy from him again?
I couldn’t possibly disagree with anything you say. I don’t work for Flowserve
The problem I face everyday is dealing with purchasing agents whose bonus plan is based on the amount of money they save. This bonus is typically based solely on initial cost of equipment. As bad as this may be it actually seems to be the current operating mentality for most of the industrial world.
I finished a short school about two months ago named “Value Pricing.” As a manufacture I have a seemingly unlimited amount of information that I can provide a customer during the operational life of their equipment. This information can change a catastrophic failure and replacement into nothing more than a scheduled repair. For an end user this becomes a question of the value of information. The problem I have is information cost money. If brand-X has a lower cost they get the sale!
It would be great to find a way to get manufactures, purchasing agents and operations all on the same page.
It's a stray from seals, but interesting. There is an equalizer, it's in the form of warranty, and a suppliers ability to stand behind it. There are many reasons why a purchaser may want to reduce his investment. An astute purchaser will shop and compare, and draw conclusion from thier experiences. Suppliers that have high pripriotory concepts may be imune from competition, but those in comodities will be price driven. How do you convince purchasers of value, sell them in service, typically in the form of warranty. Then live up to the claim.
